can't ping single host

[rkmorrow]

I have a win2k laptop computer on a subnet trying to reach an ibm mainframe. The computer has connected to the mainframe in the past.

The client goes to a hub with a 1600 router then via point-to-point line to a 2600 router to a switch. The mainframe is connected to the switch.

laptop---1600----2600---switch---mainframe

The laptop has suddenly lost ip connection to the mainframe. Everything else on the subnet that the mainframe is on, will connect to the laptop. It is only the single ip address that she cannot ping. When I change HER ip address, she can connect again to the mainframe. No one else in eight different routed locations has a problem connecting to the mainframe. When I did a traceroute from her machine to the mainframe, the packet gets to the serial interface of the 2600, but dies at the ethernet interface where the switch is connected to the mainframe.

The only thing I can think of is a hardware address issue with her ip address on the switch in the mainframe location. connectivity after changing the ip address tells me it isn't a route table issue.

Any ideas would be appreciated.

rk

 

[rsivanandan]

Hi,

What kind of access-lists do u have on the 2600 router and also please see if you can see the MAC address of the laptop in the switch's cache (what kind of switch, for cisco, you could use "show cam&quot.

Cheers,
Rajesh

 

[nivasi]

Hi..

Ensure wether relevelent route is available in 2600 router or not , if not try to put that ..

One more thing i want to know that in 2600 router u r using static route are dynamic routing ..?

ensure that is there any traffic filtering in that router config..ok


Nivas

 

[bierhunter]

I wouldn't worry about a hardware address issue on the switch in the mainframe area. MAC addresses don't pass through routers, so the laptop's MAC address isn't known to any device outside of its own subnet.

You mention that when you change the IP addres the client works ok. What are you changing it to, and what are you changing it from?

On the laptop, is the IP address, subnet mask, gateway all correct? Does the information match that of the 1600 router's interface?

Something to check from the laptop: Can you ping the gateway (the 1600 router). Can you ping the router's farside interface? The interface connecting the 1600 to the 2600. If no, then your problem is within that scope of the network.

 

[rkmorrow]

I realize the switch will not have the hardware address of the computer on the remote network, I was thinking maybe it could have the ip address mapped to a different hardware address.

If not, the problem must be the mainframe arp cache?

 

[bierhunter]

Let's take this to a basic level.

Go to the PC with the problem and ping everything. What can it ping and what can it not ping? That's a simple layer 3 test. Remember the OSI layers. If you are stuck at a lower layer, then the layers above that are irrelevant. You have to work your way up. Can you talk between all machines at layers 1 through 3?

The arp cache involved before should be cleared by now, or something's not configured right; so the arp cache shouldn't be an issue.

 

[Randomnoise]

If this Persdon used to be able to connect, but now she cannot, then something has changed, I would first find out if any configuration Work has taken place prior to the date of this occurance.